Fan girls are a particular group of the human species usually characterized by high-pitched shrieks and spontaneous crying in the presence of the opposite sex. Assuming that opposite sex is a boy band member, cuz OMG Harry Styles iz SooOOOooo hawt!

David Attenborough has spent his career narrating nature documentaries about the world's rarest animals and now he's shifting his focus to fan girls to try to understand their behavior -- most notably why their communication must be ear-bleeding loud.